During a radio frequency therapy an alternating current will be delivered near to a nerve or into the tissue via an electrode. This current generates within the tissue an electrical field while continuously emitting heat. By the emitted heat a nerve focused on will be stimulated and/or harmed, thereby reducing the pain caused by the nerve. Furthermore, the electrical field will be routed distally into the central nervous system, thereby affecting the neuronal plasticity of the central nervous system. This achieves a further pain relief. An apparatus for application of a radio frequency therapy comprises a generator, an earth plate with cables as well as an electrode, which is inserted via a specific, non-isolated cannula.
In contrast to a conventional radio frequency therapy a pulsed radio frequency therapy will be performed at the body temperature, thus no heat damages and deafferentation pain are caused. The pulsed radio frequency therapy does not produce heat in the tissue because only every 0.5 seconds energy is delivered in small portions of 20 msec. The tissue temperature rises to a maximum of 42 degree Celsius. Via the pulsed radio frequency therapy within the nerve cells, amongst others of the posterior horn of the spinal cord, genes are activated, which leads to a damping of the afferent pain activity. The current pulse of 20 msec has for example a frequency of 500.000 Hz. The mentioned offered parameters, like the pulse width, can be modified, as long as a damaging temperature is not reached.
From the prior art special needles are known, which can be connected to a generator for a pulsed high frequency. These special needles and high frequency generators are used for a directed stimulation of nerves which cause a disposal of a pain relief substance within the spinal cord and thereof cause effect a pain treatment. The usage of these special needles is limited by the anatomical structure or is not used because of the risk of an injury during the insertion of the special needles.
From EP 1 181 947 A2 an epidural catheter with at least three electrodes in a row is known. The electrodes are used for an electrical stimulation of nerves or of the spinal cord. A channel for injection of drugs provided, so that in addition to the electrical stimulation of the spinal cord or the spinal nerves a pain relief drug can be injected.
DE 203 12 110 U1 discloses a flexible catheter, particularly an epidural catheter, which has at the proximal area at least two electrical contacts, whose supply lines are disposed within the catheter, and a temperature sensor in the proximal area, whose supply lines are also disposed within the catheter. Using the temperature sensor the stimuli caused or the temperature rise because of the applied electrical energy can be monitored.
The known apparatuses for an application of a pulsed radio frequency therapy are all designed to treat nerve tissue. For this purpose the apparatus is arranged near to the nerve, so that the electrical field preferably impacts to the nerve. Therefore the electrodes are stationary located on the catheter. Die parameters of the created electrical field can only be modified using the voltage of the generator, by changing the polarity of the voltage or by inserting another apparatus with different spacing between the electrodes.